The present invention relates to a liquid or gas flow meter which includes a rotary piston carrying at least one magnet, and a magnetic transducer.
In a known flow meter (see for example U.S. Pat. No. 3,874,235) which comprises a rotary piston carrying a magnet and a magnetic transducer, the magnetic field-sensitive parts are arranged at the center of the path of motion of the exciter magnet and are provided with U-shaped magnetic conductor strips for guiding the magnetic field lines, the poles of which are diametrically opposite each other in the path of motion. To increase measuring accuracy, several poles are provided in this type of flow meter. However, the central arrangement of the magnetic field-sensitive parts at the center of the path of motion and the relatively large dimensions of the poles and the magnetic conductor strips require narrow tolerance limits in order to increase measuring accuracy for reasons of space. If relatively numerous, closely adjacent poles are arranged, there is a further danger of spuriously generated signals by the magnetic field-sensitive parts.